The present invention relates to digital video test and measurement, and more particularly to high precision image alignment detection for the registration of two images.
Conventional measurement of video signals occurs in the analog, broadband domain using conventional waveform monitors and vectorscopes. As video signals move into the digital domain, using serial digital formats and compression, the digital signals are conventionally converted into the analog, broadband domain for typical video measurements. However, especially with compressed video signals, there are additional requirements on the measurement of video signals since an important aspect of compression/decompression techniques is to assure a controlled level of picture quality degradation, i.e., the decompressed video signal presents the expected quality of display related to the video signal prior to compression.
The PQA200 Picture Quality Analysis System, manufactured by Tektronix, Inc. of Wilsonville, Oreg., is a programmable instrument for automatic measurement of compressed video quality, and is described in allowed U.S. patent application Ser. No. 08/605,241 filed Feb. 12, 1996 by Bozidar Jenko et al. The PQA200 adds stripes and registry marks to the active video portion of the video signal so that, when the video signal is compressed and then decompressed, the images in the received, decompressed video signal may be aligned with the corresponding images in the video signal prior to compression. The precision of this alignment process is important to provide the most accurate determination of picture quality.
What is desired is a high precision image alignment detection technique to assure that corresponding images to be measured for picture quality are aligned to provide the most accurate determination of picture quality.